Greg Egan is a fantastic author and Quarantine is one of his very early books, and it shows a little. The book is full of the usual wonders of Egan's ideas but I felt that the ending was a little weak. I couldn't say why, there was no good reason why it wasn't a good ending - had a neat little twist and there weren't any loose threads left, but I felt like it didn't quite get back to the home key (GEB reference, for those who get it).